Technical Field
The present application relates generally to touch devices, and more specifically to systems, methods, and devices for reducing shadow effects in touch systems.
Background
Advances in technology have resulted in smaller and more powerful computing devices. For example, there currently exist a variety of portable computing devices, including wireless computing devices such as wireless telephones, personal digital assistants (PDAs), and tablet computers that are small, lightweight, and easily carried by users. In order to simplify user interfaces and to avoid pushbuttons and complex menu systems, such portable computing devices may use touch screen displays that detect user gestures on the touch screen and translate the detected gestures into commands to be performed by the device. Such gestures may be performed using one or more fingers, or a stylus-type pointing implement, in contact with or in close proximity to a sensing surface of a computing device.
Due to the relatively coarse cross-section of an average human finger, finger-based touch input can be used for operating coarse controls on the user interface, such as selecting an item or pressing a button. Use cases such as on-screen drawing, calligraphy, or hand-writing capture for example, may require a fine-tipped input tool or stylus to allow the touch sensitive surface to capture finer movements. In some aspects, when a stylus is tilted, the hovering effect creates a shadow in the touch signal that makes the touch signal asymmetric. Since the stylus's signal may be weaker than a finger-based signal, the shadow may have a significant impact on stylus accuracy and make the estimated stylus trajectory unstable. Thus, systems and methods for reducing the shadow effects in touch systems are needed.